what are the most weightage chapters in biology to score most marks in neet ?

You can check the topic and percentage below -

Biological Classification 10
Principles of Inheritance and Variation 7.8
Morphology of Flowering Plants 6.7
Cell: The Unit of Life 6.7
Animal Kingdom 4.4
Reproduction 11
Ecosystems 4.4
Molecular Basis of Inheritance 3.3
Human Health and Diseases 3.3
Body Fluids and Circulation 3.3
Neural Control and Coordination 2.2
Biotechnology: Principles and Processes 2.2
Anatomy of Flowering Plants 2.2
Locomotion and Movement 2.2
Microbes in Human Welfare 2.2
Photosynthesis 2.2
Chemical Coordination and Integration 2.2
Evolution 2.2
Excretory Products and Their Elimination 2.2 Biomolecules 2.2
Organisms and Populations 2.2
Structural Organization in Animals 1.1
Cell Cycle and Division 1.1
Biotechnology and its Applications 1.1
Strategies for Enhancement in Food Production 1.1 Digestion and Absorption 1.1
Transport in Plants 1.1
Mineral Nutrition 1.1
Breathing and Exchange of Gases 1.1
Plant Growth and Development 1.1

Hope this helps!!!!

You have to focus on Plant & Human Physiology,Reproduction,Genetics & Biotechnology.Almost 60% questions are from these sections.

Here are some weightage topics you can prefer to prepare:

PHYSICS

• Rotational motion
• Thermodynamics
• Properties of bulk matter
• Oscillation & Waves
• Electrostats
• Magnetism whole unit
• Modern physics
• Ray & wave optics
• Semiconductor

CHEMISTRY

• Thermodynamics & equilibrium
• States of matter
• Chemical bonding
• Chemical kinetics
• Basic concept of organic chemistry
• Inorganic chemistry of 12th class
• Organic chemistry of 12th class

Biology

1. Human Physiology
2. Human Reproduction
3. Biotechnology
4. Cell Biology
5. Genetics

Also you can refer to previous year sample papers for more idea of topics and practice.